Thermoregulator.



c. P. STEINMETZ.

THERMOREGULATOR. APPLLCATION FILED JUNE 26.1917.

1 ,276, 5 89 Patented Aug. 20, 1 918.

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II'ULL UNITED sTATE-s PATENT OFFICE.

CHARLES P. STEINMETZ, 0F SCHENECTAIDY, NEW YORK, ASSIGNOR '10 GENERAL ELECTRIC COMIPANY,

A CORPORATION OF NEW YORK.

THEBMOREGULATOR.

To all whom it may concern:

Be it known that I, CHARLES P. STEIN- METz, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Thermoregulators, of which the following is a specification.

My invention relates to the temperature control of a device which in its operation evolves heat and it has for its object the improvement of a device of this character.

The device, the temperature of which is to be controlled in accordance with my invention, may be one whose function is the production of heat, or it may be one in which the production of heat is incidental.

My invention will best be understood reference to the accompanying drawings, 11]. which, Figure 1 is a diagrammatic view showing one embodiment of my invention applied to the control of a heating device;

Figs. 2, 3 and 4 are modifications of l5 ig.- 1;

' and Fig. 5 is a diagram showing my lnvenferent temperature tion used for controlling the temperature of. a vacuum lightning arrester. Referring now to the drawings, and first to Fig. 1,.10 is a device the temperature of which is to be controlled as for example an electric heater. The electric heater is supplied with current from a generator 11, through a Wheatstone opposite resistance legs of which 12 and 13 have a given temperature coeflicient, while the remaining two legs 14 and 15 have a difcoefiicient from the legs 12 and 13; preferablylegs 12 and 13 hav e a positive temperature coeflicient and may be made for instance of iron, and the legs 14 and 15 a negative temperature coefiicient,- and may be formed of a material such as silicon or may be made of an electrolyte. The junction points of the "various resistances are indicated by the numerals 16, 17, 18 and 19. 'All.,.of' the resistance elements of the Wheatstone bridge are externally aflecte'd by the heat evolved byv the heating device, and are intended to maintainthe temperature thereof substantially constant. It will, of course, is the temperature of the space surrounding the heatingdevice whose tem erature is controlled; but since this is a notion of the temperature of the heating device, have,

for con enience, reierred to the arrangement stone bridge.

bridge A, two of theing device attaining a be understood that, strictly, it

as controlling itself. -The elements of the Wheatstone bridge are so arranged that, at the temperature which they attain when the heating device isv operated at the desired temperature,

equal. ture of the heating device'and correspondingly that of the resistance elements Wheatstone bridge is below that at which the device is intended to operate, then the Specification of Letters Patent. Patented Aug. 20, 191-8. Application filed June as, 1917. Seria11i'o. 176,965.

the temperature of the device their resistances are substantially Assuming now that" the temperaof the,

resistances of the elements 12 .and 13 of the Wheatstone bridge having a positive tern-f perature coefficient will be low as compared with the-resistances-of the elements 14 and 15 which have a negative temperature coeflicient. Assuming further that the positive terminal of the generator is the oneadjacent to the Wheatstone bridge, then, since;-

the drop 'in voltage across the resistances having the positive temperature coeflicient is less than the drop across the resistances having the negative temperature coefficient, the

point 17 will be at a higher voltage than the point 16, and a current will flow from the terminal 17 to the terminal 16 through the heating element 10 and raise the temperature thereof and correspondingly raise the temperature of the elements of the Wheatthrough .the heating ture thereof, as well as that of resistance elements themselves will continue 'to rise until there is no voltage, voltage between the points 17 and 16 which will be the temperature at which it is desired to operate the heating device.

is included in the ,local' circuit of the heating Current will continue to flow device and the temperaf or practically no.

Preferablya unidirectional cell 20, such for instance as I arranged that current. passes freely ther'e- .1

through in one direction, in order to raise the temperature of the heating device toth'e desired point, but prevents passage of cur.

rent in the opposite direction in case there should be any such tendency due to the heatthat at which it is'desired to operate.

With the arrangement temperature of the space surrounding the It will be apparent, however, ably arranging same arrangement may be used to maintain the temperature of the heatin here described, the 5.

device above temperature above flow and the temperature of the device be maintained above predetermined minlmum;

One application of this latter arrangement is in the heating of aluminum cell lightning arresters which are placed in out door substations or in such exposed positions that there is danger of their freezing. In this case the unidirectional cell and cooperating elements would be so arranged that when the temperature of the space surrounding the arrester was above freezing no current would flow through the heater, and as soon as it dropped-below f-reezing, current would flow itherethrough.

The system shown in Fig.2 operates similarly to that shown in Fig. 1, but in this case the heating device 10 is controlled by a relay 21, which is included in the local air-- cuit derived from the Wheatstone bridge, the armature 22 of which controls thecircuit to the heating device in this case through another relay 23 and its armature 24, the heating device being connected to a separate supply circuit which is indicated 30 I by the reference numerals 25 and 26.

In the arrangement shown in Fig. 3, the

heating device is controlled by a polarized" relay 27 included in the local circuit derived from the Wheatstone bridge, the magnetic armature of which carries a contact which makes contact with either of two stationary contacts 29 or 30, controlling circuits to two magnets of the relay 23 which are designed to positively open and close the circuit of the heating device. In this case, no unidirectional cell. is included in the local circuit derived from the .Wheatstone bridge, and when the device is below a predetermined temperature, current will flow through the relay 27 in one direction to attract the armature and throw'the contact 28 into engagement with the contact 30 and thus close the circuit of the heating device, whereas when the heating device is above the desired temperature, current will flow through the polarized relay 27 in the opposite direction and repel the armature and bring the contact 28 into engagement with the contact 29 and thus open the; circuit ofthe heating device, the armature being held in either extreme position by a light over centermg spring as shown.

In the modification shown in Fig. 4, the heating element 10is controlledby. two relays. 21 and 21 included in two difi'ere'nt circuits derived from the Wheatstone bridge. The relay 21 through its armature mg device 10 .whenthe same is energizecil,

through the relay '21 to actuate the same,

while the relay 21 correspondingly opens the circuit thereof.

My invention is useful not only for controlling the temperature of a heating (16-. vice, but may be used for controlling the temperature of a device in which the production of heat is incidental, and thus prevent. injury thereto. In Fig. 5 I have illustrated my invention in connection with a vacuum lightning arrester. As is well known, these devices sometimes become overheated, due to? a continuous discharge, and the arrangement here-shown is utilized to close a short circuit around the arrester under such conditions. The control is effected by a relay 21 included in a local circuit derived from the Wheatstone bridge A in precisely the same manner as described in connection with Fig. 2. When the light ning arrester reaches a predetermined temperature, and correspondingly the elements of the VVheatstone bridge which are subjected to the temperature of the lightning arrester, a sufficient current will pass and through the relay 23 close a shunt around the vacuum lightning arrester 31, provided with the usual electrodes 32 and 33', which are connected to conductors in any desired circuit, such as a telephone system. I

While I have described my invention as embodying'a concrete structure and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be. understood that I do not limit my invention thereto, since various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope f which is set forth in the annexed claims. What I claim as new and desire to secure by Letters Patent of the Unitedbtates, is 1. In combination, a device which develops heat during its operation, a source of energy connected to said device, and means for controlling the energy supplied to said device comprisingresistances having difi'erent temperature coeflicients and which are affected by the heat developed by said device, the resistances being balanced at a pre determined temperatur I 2. In combination, a device which devel ops heat during its operation, a source of electrical energy, andmean's for controlling the energy suppl to said, device comprising a Wheatstone bridge, the legs of which are formed of resistances having different temperature coeflicients all of the resistances of the Wheatstone bridge being subjected to the temperature of said deviceand the resistances being balanced at a predetermined temperature. 3. In combination, a device'which 'devel-.- ops heat during its operatioma source of 130 energy connected to said device, and means for controlling the energy supply to said device comprising a VVheatstone bridge two of the opposite elements of which have a positive temperature coefiicient and the other resistance elements a negative temperature coefiicient, the resistances being balanced at a redetermined temperature.

4. In com ination, an electrlc heating de* vice, a source of electric energy supply connected thereto, and means comprlsing a ll heatstone bridge, two of the opposite legs vice, a source of electric energy supply connected thereto, and means comprising a Wheatstone bridge, two of the opposite legs of which have a positive temperature coefficient and the remaining two a negative temperature coeflicient for controlling the energy supplied to said device.

6. In combination, a device which develops heat during its operation, a source of energy connected to said device, and means for controlling the energy supplied to said device comprisinga Wheatstone bridge, two

' of the opposite legs of which have a positive temperature coefficient and the remaining two a negative temperature coefficient, and a circuit including a unidirectional cell connected to opposite junction points of the IVheatstone bridge.

In witness whereof, I have hereunto set my hand this 25th day of June, 1917.

CHARLES P. STEINMETZ. 

